Stem cells are pluripotent or totipotent cells that can differentiate in vivo or in vitro into many or all cell lineages. Due to their pluripotency, embryonic stem (ES) cells hold great promise for treating degenerative or inherited diseases. Yet, ethical considerations have hampered the use of human ES cells. Stem cells of a non-embryonic origin would circumvent this obstacle. These adult stem cells have the same capability for differentiation as do ES cells.
Multipotent adult progenitor cells from bone marrow have been isolated that can differentiate into ectoderm, mesoderm and endoderm. Other types of cells, including marrow-isolated adult multi-lineage inducible cells and single cell clones derived from bone marrow also have the same multi-potential ability for differentiation. Such multipotent somatic cells are difficult to obtain, culture, and expand.
Thus, there is a need for adult somatic stem cells that can be easily isolated and maintained.